Is it possible to have a property sensor detect a value higher or lower than a specific number?
You mean like "Less than"?



A value less than 1 is either equal to or less than zero.

EDIT: the options for evaluating properties "Less Than" and "Greater Than" was added in blender 2.71. Previous versions don't have these options.

The easy solution would be to upgrade to 2.71, another option would be to use a python controller to do the test of the property value.